Antiperspirant compositions are well-known in the cosmetic art. An ideal antiperspirant composition is stable for the life of the composition, effectively delivers the antiperspirant compound to the skin, does not leave a visually-observable white residue on the skin or clothing, and is esthetically pleasing to the consumer.
Antiperspirant compositions are available in a variety of forms, such as aerosol suspensions; pump sprays; roll-on powders; emulsions or suspensions; and solid gels, waxes or suspensions. Antiperspirant compositions traditionally have been prepared as either oil-in-water emulsions or water-in-oil emulsions. Therefore, antiperspirant compositions of any form typically have a milky or opaque appearance and are manufactured by complex methods. Antiperspirant compositions prepared as emulsions often feel wet or oily when applied to the skin, and often remain tacky after the carrier of the composition evaporates. In addition, many emulsion-type antiperspirant compositions leave a white, staining residue on contacted skin or clothing.
Gelled emulsion-type antiperspirant compositions are used by rubbing an area of the body, such as the underarm, to apply a layer of the composition to the skin, and thereby reduce odor and/or perspiration. Gelled or solid antiperspirant compositions preferably possess the esthetic properties of nonbrittleness, smoothness, nonoiliness and nontackiness. Clarity, or transparency, of antiperspirant compositions also is a long-sought desirable esthetic property. Another highly desirable, but hard to achieve, esthetic property is avoiding a visible residue, e.g., a white layer, that is left on the skin or clothing after the antiperspirant composition is applied.
Nonemulsified antiperspirant compositions also are known in the art. However, nonemulsified compositions often require shaking prior to each use in order to redisperse the insoluble antiperspirant compound that has separated from the composition. Nonemulsified antiperspirant compositions that do not require shaking prior to each use, such as an antiperspirant creme or paste, typically include a relatively high percentage of suspending agents, like an organoclay. The presence of an organoclay in an antiperspirant composition is a principal source of the whitening and staining of skin and clothing.
Investigators have searched for antiperspirant compositions, and especially transparent antiperspirant compositions, that display the above-listed desirable properties. A gelled or solid antiperspirant composition is difficult to formulate and manufacture because the composition requires sufficient firmness to withstand rubbing across the skin to deliver a sufficient amount of the antiperspirant compound to the skin, and the composition also should be nonbrittle to resist fracturing and crumbling. Additional formulation parameters include viscosity control, lack of syneresis and nontackiness. Transparent, gelled or solid antiperspirant compositions are more difficult to formulate because of the added requirement of transparency.
A transparent gelled or solid antiperspirant composition which has esthetic and functional properties equal to or better than presently-available antiperspirants compositions is highly desired by consumers. However, providing a commercially-acceptable, transparent gelled or solid antiperspirant composition requires overcoming several formulation and manufacturing problems.
Transparent antiperspirant compositions, especially in the gel or solid, i.e., stick, form, are particularly favored by consumers because such transparent products are esthetically-appealing and project the appearance of product purity, safety, good performance and being non-whitening. However, due to the instability and the difficult manufacture of transparent compositions, transparent antiperspirant compositions are not readily available to consumers.
Solid antiperspirant compositions are divided into three main classes, i.e., compressed powder sticks, gel sticks and wax sticks. Each of these classes has advantages, but each class also has particular disadvantages. Compressed powder sticks for example are frequently brittle and hard, and leave a cosmetically-unacceptable powdery residue after application. Frequently, wax-based products are cosmetically unacceptable because of such factors as hardness, greasiness and tackiness. The opacity of wax sticks and the visually-observable white residue remaining after application also are esthetically undesirable.
Gel-type solid antiperspirant compositions have several advantages over both compressed powder sticks and wax sticks. For example, the gelled antiperspirant compositions leave less residue or dust on the skin. The gelled antiperspirant compositions also glide easily over the skin surface resulting in an easy and comfortable application of the composition.
However, the preparation of antiperspirant compositions in the form of an effective and stable gel is difficult. For example, a critical ingredient in gelled antiperspirant compositions is the gelling agent. Many prior gelled antiperspirant compositions comprise gelled hydroalcoholic solutions including a gelling agent, such as sodium stearate, to form the gel. However, common gelling agents cannot be used in the presence of acidic antiperspirant compounds because of an interaction between the gelling agent, which is alkaline, and the antiperspirant compound.
Prior transparent, gelled or solid antiperspirant compositions also typically were divided into three main classes. One of these classes is the optically-clear gelled emulsion compositions. These compositions include a water phase and an oil phase. The oil phase is suspended in the water phase by using a sufficient amount of an appropriate emulsifier or emulsifiers. The emulsions conventionally contained waxes, silicones, clays and emollients. The optically-clear gelled emulsion compositions are illustrated in U.S. Pat. Nos. 4,673,570, 4,268,499, 4,278,655, and 4,350,605; EP 0 450 597; and in "Deodorant and Antiperspirant Formulary", Cosmetics & Toiletries, Dec. 12, 1985, vol. 100, p. 65-75.
The optically-clear gelled emulsion compositions often exhibit the disadvantages of composition instability during storage; the development of a hazy or milky appearance during storage; a stringy, tacky, oily consistency and other undesirable esthetics. In addition, the emulsion gel compositions often leave a visible residue, in the form of a white layer, on the skin or clothing. Another disadvantage of optically-clear gelled emulsion compositions is the complex method of preparing an optically-clear gelled emulsion composition. The method traditionally requires high shear rates during mixing, high processing temperatures, and a series of cooling and heating process steps. In one embodiment of the present invention, optically-clear gelled emulsion compositions are prepared by a simple method to provide antiperspirant compositions that overcome the above-described disadvantages of optically-clear gelled emulsion compositions.
A second class of transparent gelled or solid antiperspirant compositions is antiperspirant compositions thickened with 3:2,4-dibenzylidene-sorbitol (DBS) or DBS derivatives. Such transparent antiperspirant compositions are disclosed in U.S. Pat. Nos. 4,822,602 and 4,725,430; European Patent Publication 0 512 770; WO 91/15191; and WO 92/19222.
Transparent, gelled antiperspirant compositions thickened with DBS or DBS-type compounds have a major disadvantage in that the compositions are unstable in the presence of highly-acidic antiperspirant compounds at elevated temperatures. In addition, another disadvantage is the high temperature required for manufacturing DBS-thickened compositions (i.e., about 230.degree. F. to about 240.degree. F.).
The third class of transparent gelled or solid antiperspirant compositions is the acid-base complex gels. These transparent antiperspirant compositions are prepared by interacting the active antiperspirant compound with a carboxylic acid salt. Transparent acid-based complex gels are disclosed, for example, in U.S. Pat. Nos. 3,255,082 and 2,876,163; and in European Publication No. 0 448 278. Govett et al. U.S. Pat. Nos. 2,607,658 and 2,654,616 disclose a gel comprising an aluminum chlorohydroxy complex and a borate.
For example, EP 0 448 278 discloses complexing an antiperspirant aluminum salt with ammonium acetate. U.S. Pat. No. 2,876,163 discloses complexing an antiperspirant aluminum salt with various water-soluble inorganic salts, like an alkali metal oxide, hydroxide, or carbonate, or a salt of an organic or inorganic acid, such as sodium carbonate, sodium phosphate, or sodium glutamate.
This third class of transparent antiperspirant compositions has a major disadvantage in that the active antiperspirant compound is partially deactivated by the salt, thereby reducing the efficacy of the antiperspirant compound and, accordingly, the antiperspirant composition. In addition, the resulting gels or solids are very brittle, tacky, and/or possess other undesirable esthetic properties, such as in the compositions disclosed in U.S. Pat. No. 3,255,082, which are emulsions or sols and therefore are often opaque.
Although numerous patents disclose transparent gelled or solid antiperspirant compositions, the gelled compositions designated as clear or transparent do not have the clarity desired by consumers. Some transparent antiperspirant compositions also exhibit syneresis, or phase separation, during storage. Moreover, many of the prior art transparent compositions become cloudy or hazy after standing for a period of time. Typically, haziness increases to such an extent that the composition is cloudy and has little or no transparency about a month after preparation. Antiperspirant compositions conventionally have a product life in excess of one month. Therefore, the length of time the composition retains its transparency is an important esthetic property.
Investigators have continually sought to provide a gelled or solid antiperspirant composition having both long-term stability and sufficient esthetic and functional properties for consumer acceptance. These esthetic and functional properties include transparency, a sufficient hardness for application to the skin, a low degree of brittleness to resist fracture and crumbling of the composition, no visually-observable whitening of the skin and clothing, and the ability to effectively deliver the antiperspirant compound to the skin without providing a tacky or sticky feeling. The present invention is directed to providing gelled or solid antiperspirant compositions, and preferably transparent compositions, exhibiting these consumer-acceptable esthetic and functional properties.